The present invention relates generally to apparatus and methods for use in treating proliferative tissue disorders, and more particularly to apparatus and methods for the treatment of such disorders in the body by the application of radiation to a tissue surface.
Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it. Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary interstitial brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a spatially confined radiation source inserted into the body at or near a tumor or other proliferative tissue disease site. Owing to the proximity of the radiation source, brachytherapy offers the advantage of delivering a more localized dose to the target tissue region.
For example, brachytherapy is performed by implanting radiation sources directly into the tissue to be treated. Brachytherapy is most appropriate where 1) malignant tumor regrowth occurs locally, within 2 or 3 cm of the original boundary of the primary tumor site; 2) radiation therapy is a proven treatment for controlling the growth of the malignant tumor; and 3) there is a radiation dose-response relationship for the malignant tumor, but the dose that can be given safely with conventional external beam radiotherapy is limited by the tolerance of normal tissue. In brachytherapy, radiation doses are highest in close proximity to the radiotherapeutic source, providing a high tumor dose while sparing surrounding normal tissue.
One example of a brachytherapy device is disclosed in U.S. Pat. No. 5,030,195 of Nardi, entitled “Radioactive Seed Patch for Prophylactic Therapy.” Nardi describes a method and apparatus for treating tissue surrounding a surgically excised tumor with radioactive emissions to kill any cancer cells that may be present in the tissue surrounding the excised tumor. In order to implement the radioactive emissions, Nardi provides a low-energy, nonabsorbable radioactive seed patch made from a plastic mesh having Iodine-125 seeds threaded therein. The patch is put in place during the time of surgery after the resection of the tumor, and remains therein indefinitely.
While the apparatus described in Nardi provides some advantages, the patch is limited to use with permanently implanted radioactive seeds, which in some applications can be less effective than other radiation sources. Moreover, Nardi does not disclose methods for tailoring the radiation dosage to avoid fully dosing sensitive tissue or to reduce the amount of radiation that escapes into the body.
Accordingly, there is still a need for a device that can be used to effectively deliver radiation from a solid and/or liquid radioactive source to target tissue within the human body.